1. Field of the Invention
The present invention relates to an ink jet recording method used for recording an image by discharging liquid from a recording head. More particularly, the present invention relates to an ink jet recording method used for recording an image by discharging ink droplets to a recording medium from an ink jet recording head.
2. Description of the Related Art
An ink jet recording head of an ink jet recording apparatus has a heating element arranged in a recording liquid chamber. An electric pulse (i.e., a recording signal) is applied to the heating element to generate heat. Thermal energy generated by the heat causes a phase change in the ink and produces bubbles (or the ink boils). The ink liquid is discharged from a discharge port owing to a pressure generated at this time, and recording is performed on a recording medium.
In recent years, there is a demand for an ink jet recording apparatus having an ink jet recording head which is capable of producing photo quality prints at a higher speed. In addition, competition among manufacturers to lower the price of the ink jet recording apparatus is getting severe and it becomes important to manufacture products at a low cost.
U.S. Pat. Nos. 5,218,376 and 6,354,698 discuss methods for stably discharging smaller ink droplets from an ink jet recording head, which contributes to high-quality image printing. In these methods, a bubble generated by an energy generation element, which discharges the ink from the ink jet recording head, is in communication with the atmosphere.
Further, U.S. Pat. No. 7,108,352 discusses a method for manufacturing an ink jet recording head at a low cost, the recording head being configured to discharge a small droplet at a higher speed. According to U.S. Pat. No. 7,108,352, nozzles are arranged on an ink jet recording chip at a high density, and ink droplets of various discharge amounts are discharged from the ink jet recording head.
In such an ink jet recording head, relatively small ink droplets are used for a highlighted area of a recording image and larger ink droplets are used for a dark image area. As a result, high-speed and high-quality image printing can be achieved at the same time.
In order to manufacture such an ink jet recording head at a low cost, it is useful that the nozzles capable of discharging various amount of ink are formed on one ink jet recording chip. Further, in order to realize low cost manufacturing, it is useful that a nozzle plate used for forming the nozzles has even thickness. In other words, it is useful that a distance from the energy generation element for discharging ink to a top of the nozzle plate is kept constant for each of the nozzles that discharge different amounts of ink.
However, a problem arises in manufacturing the ink jet recording head that satisfies the afore-described features. In particular, when the nozzle density is increased to 900 dots per inch (dpi) or more and the distance between the liquid supply port and the heater (hereinafter referred to as CH distance) is changed, a refill frequency of the nozzles that have relatively long CH distance becomes low. The term, refill frequency, is the frequency that a temporarily emptied recording liquid chamber is refilled with ink again.
In such a case, in order to perform the refill at a high frequency as much as possible, it is useful that the CH distance of the nozzles, which discharge a relatively small amount of ink, is longer than the CH distance of the nozzles, which discharge relatively a large amount of ink. This is because, in the case of the nozzles that discharge a larger amount of ink, the amount of retreat of the liquid to the liquid supply port increases at the time of bubbling. Therefore, if the CH distance of the nozzles that discharge a larger amount of ink is long, the refill frequency is lowered, which may result in a faulty ink supply.
It is assumed, for example, that nozzles discharging a 2-pico liters (pl) ink droplet and nozzles discharging a 1-pl ink droplet are arranged alternately (staggered arrangement), and both nozzles discharge ink while a bubble generated by an energy generation element communicates with the atmosphere. In such a case, a longer CH distance is useful for the nozzles discharging a 1-pl ink droplet according to the above described viewpoint.
However, contrary to the above-described viewpoint, there happens to be a case where the refill frequency of the nozzles discharging a 1-pl ink droplet becomes lower than the refill frequency of the nozzles discharging a 2-pl ink droplet. This may cause a negative impact on high-speed recording.